the air bag light is on in my 2000 buick regal i think the air bag in the seat was deployed how can i fix and will it cost me a lot.

Not sure what you mean by " I think the air bag in the seat was deployed " ? Does you car have the side seat air bags ? If so , have they been deployed and are now hanging from the side of the seat ? I think we need more info before we can possibly help .

well the air bag light is on and when i was cleaning the seats on the side it has a cover that says air bag and is held shut with a piece of tape so i think they have been deployed because i think i should not be like that?

There are only two air bags in this Regal. The driver's side at the steering wheel and passenger side at the top of the dash. If the airbag warning light is on then it is failing diagnostics. It needs to be scanned with a scan tool capable of reading out SIR/SRS codes like a GM Tech 2.

If you did any cleaning under the passenger side seat then check the wiring and connectors to the SDM module which is the brain of the air bag system.